During the completion process of a hydrocarbon-producing well in a subterranean formation, a conduit, such as a casing string, may be run into the wellbore to a predetermined depth and, in some instances, cemented in place to secure the casing string. Various “zones” in the subterranean formation may be isolated via the placement of one or more packers, which may also aid in securing the casing string and any completion equipment, e.g., fracturing equipment, in place in the wellbore. Following the placement and securing of the casing string and any completion equipment in the wellbore, a “pressure test” is typically performed to ensure that a leak or hole has not developed during the placement of the casing string and completion equipment.
Generally, a pressure test is conducted by pumping a fluid into a flowbore of the casing string, such that a predetermined pressure, typically related to the rated casing pressure, is applied to the casing string and completion equipment and maintained to ensure that a hole or leak does not exist in either. To do so, the casing string is configured such that no fluid passages out of the casing string are provided; thus, no ports or openings of the completion equipment, in addition to any other potential routes of fluid communication, may be open or available. After the pressure test is completed, further completion or production of the hydrocarbon-producing well may commence.
Accordingly, in order to either retrieve hydrocarbons and other fluids from the subterranean formation or to stimulate the subterranean formation, for example, via fracturing, one or more flow paths may be created to provide communication between the flowbore and the wellbore or subterranean formation, or both, through the casing string. One method of providing such flow paths includes the utilization of a perforating gun. In such a method, a perforating gun, typically including a string of shaped charges, is run down to the desired depth on, for example, E-line, coil tubing, or slickline. The shaped charges are detonated, thereby creating perforations in the casing string and hence the flow paths between the subterranean formation, wellbore, and the flowbore. However, one disadvantage of perforating is “skin damage,” where debris from the perforations may hinder productivity of the hydrocarbon-producing well. Another disadvantage of perforating is the cost and inefficiency of having to make a separate trip to run the perforating gun downhole.
Accordingly, in an effort to reduce the number of trips, another method of providing such flow paths includes the utilization of a pressure activated tool, such as a differential valve, in the casing string. Generally, the differential valve is designed to open, creating such flow paths, once a threshold pressure is reached; however, the differential valves generally may often be inaccurate as to the pressure at which they open and such valves also do not allow for closing once they have been opened. Thus, once a pressure test has been performed at or near the threshold pressure, the well will be open, thereby impairing or potentially eliminating the ability to control the wellbore, thereby posing various risks, such as blow-outs or the loss of hydrocarbons.
What is needed, then, is a downhole completion tool capable of undergoing a pressure test and subsequently providing flow paths for production or stimulation fluids while maintaining wellbore control after the pressure test is completed.